The preferred embodiments of the present invention generally relate to an electrical connector assembly having a receptacle connector mateable with a header connector, in a small envelope and with high signal performance characteristics.
It is common, in the electronics industry, to use right angled connectors for electrical connection between two printed circuit boards or between a printed circuit board and conducting wires. The right angled connector typically has a large plurality of pin receiving terminals and, at right angles thereto, pins (for example compliant pins) that make electrical contact with a printed circuit board. Post headers on another printed circuit board or a post header connector can thus be plugged into the pin receiving terminals making electrical contact there between. The transmission frequency of electrical signals through these connectors is very high and requires not only balanced impedance of the various contacts within the terminal modules to reduce signal lag and reflection but also shielding between rows of terminals to reduce crosstalk.
Impedance matching of terminal contacts has already been discussed in U.S. Pat. Nos. 5,066,236 and 5,496,183. Right angle connectors have also been discussed in these patents, whereby the modular design makes it easy to produce shorter or longer connectors without redesigning and tooling up for a whole new connector but only producing a new housing part into which a plurality of identical terminal modules are assembled. As shown in the ""236 patent, shielding members can be interposed between adjacent terminal modules. An insert may be used to replace the shield or a thicker terminal module may be used to take up the interposed shielding gap if the shielding is not required. The shield disclosed in the ""236 patent is relatively expensive to manufacture and assemble. The shielded module disclosed in the ""183 patent includes a plate-like shield secured to the module and having a spring arm in the plate section for electrically engaging an intermediate portion of a contact substantially encapsulated in a dielectric material. The shield arrangement of the ""183 patent, however, requires sufficient space between adjacent through-holes of the board to avoid inadvertent short circuits. Furthermore, both the insulated module and the shield must be modified if the ground contact is to be relocated in the connector.
An alternative electrical connector assembly has been proposed in U.S. Pat. No. 5,664,968, in which each terminal module has a plurality of contacts including a mating contact portion, a connector connecting portion and an intermediate portion there between with some or all of the intermediate portions encapsulated in an insulated web. Each of the modules has an electrically conductive shield mounted thereto. Each shield includes at least a first resilient aim in electrical engagement with a selected one of the contacts in the module to which the shield is mounted and at least a second resilient arm extending outwardly from the module and adapted for electrical engagement with another selected contact in an adjacent terminal module of the connector assembly.
Conventional connector assemblies, such as in the ""236, ""183 and ""968 patents, are typically designed for use both in single ended applications as well as in differential pair applications. In single ended applications, the entire signal is directed in a first direction along one conductor and then the entire signal is subsequently returned in the opposite direction along a different conductor. Each conductor is connected to a contact within a connector assembly, and thus the entire signal is directed in a first direction through one pin or contact and in the opposite direction through a separate pin or contact. In differential applications, the signal is divided and transmitted in the first direction over a pair of conductors (and hence through a pair of contacts or pins). The return signal is similarly divided and transmitted in the opposite direction over the same pair of conductors (and hence through the same pair of pins or contacts).
The differences in the signal propagation path of single ended versus differential pair applications cause differences in the signal characteristics. Signal characteristics may include impedance, propagation delay, noise, skew, and the like. The signal characteristics are also effected by the circuitry used to transmit and receive the signals. The circuitry involved in transmitting and receiving signals entirely differs for single ended and differential applications. The differences in the transmit and receive circuitry and the signal propagation paths yield different electrical characteristics, such as for impedance, propagation delay, skew and noise. The signal characteristics are improved or deteriorated by varying the structure and configuration of the connector assembly. The structure and configuration for connector assemblies optimized for single ended applications differ from connector assemblies optimized for use in differential pair applications.
Heretofore, it has been deemed preferable to offer a common connector assembly useful in both single ended and differential pair applications. Consequently, the connector assembly is not optimized for either applications. A need remains for a connector assembly optimized for differential pair applications.
Moreover, most connector assemblies must meet specific space constraints depending upon the type of application in which the connector assembly is used while maintaining high signal performance. By way of example only, certain computer specifications, such as for the Compact PCI specification, define the dimensions for an envelope in which the connector assembly must fit, namely an HM-type connector which represents an industry standard connector. However, the HM connector does not necessarily offer adequate signal performance characteristics desirable in all applications. Instead, in certain applications, higher signal characteristics may be preferable, such as offered by the HS3 connector offered by Tyco Electronics Corp.
However, certain conventional connectors that offer higher signals characteristics may not satisfy the envelope dimensions of an HM type connector standard. For example, an HM connector is designed to be mounted on the edge of a printed circuit board to connect the printed circuit board at a right angle to a daughter card. The HM connector includes a mating face that straddles the edge of the printed circuit board. The side of the HM connector is L shaped and affords a mating face located both above and below the printed circuit board surface. The contacts on an HM connector are staggered to straddle the edge of the printed circuit board. Certain types of connectors that offer high signal characteristics include contacts only along one side of the board, not staggered on either side of a printed circuit board.
By way of example only, certain convention al connectors, such as the HS3 connectors, include ground shields and signal contact terminals. The ground shields are located in the header connector and engage ground contacts in the receptacle connector when the header and receptacle connectors are joined. When mating the header and receptacle, it is preferable that the ground contact and ground shields engage one another before signal contacts in the header and receptacle engage one another.
However, in conventional connector assemblies, in order for tips of the ground contacts to engage the tips of the ground shields first, they should be longer than the signal contacts. The ground contacts and shields touch, when the header and receptacle are only partially mated. As the header and receptacle are further joined to the fully mated position, the point of connection between the tip of the ground contact and the ground shield moves from the tip of the ground shield toward the base of the ground shield. When fully mated, the tip of the ground contact is in electrical contact with the ground shield at a point proximate the base of the ground shield.
The signal performance is inferior for connector assemblies, in which the ground contact electrically engages the ground shield only proximate the base of the ground shield since the outer portion of the ground shield functions as a stub antenna to transmit electromagnetic (EM) interference. The EM interference caused by the ground shield interferes with the signal characteristics of the connector assembly.
A need remains for an improved connector assembly capable of satisfying small envelope dimensions, while affording high quality signal performance characteristics.
At least one preferred embodiment of the present invention provides an electrical connector assembly having a receptacle connector mateable with a header connector in a small envelope while affording high quality signal performance. The assembly includes an insulated housing and a plurality of terminal modules mounted to the insulated housing. Each terminal module has an insulated molded body enclosing multiple connector contacts having opposed mating portions. Each terminal module includes contacts formed into at least one differential pair. The connector assembly further includes module ground shields mounted to and located between the terminal modules. Each module ground shield includes at least one ground contact pair located proximate at least one differential pair of connector contacts. The ground contact pair includes a primary ground contact extending a first distance from the module ground shield and a secondary ground contact extending a second distance from the module ground shield.
In accordance with at least one alternative embodiment, the module ground shield includes a main body portion with a first edge along one side adapted to mate with a printed circuit board and a second edge adjacent to the first edge. The second edge is adapted to be mounted in the insulated housing. Each terminal module may comprise a lead frame that includes conductive leads arranged in at least two pairs of leads. Each lead may include connector contacts at opposite ends thereof and be interconnected through intermediate conductive portions. Each terminal module may comprise a lead frame comprised of four differential pairs of conductive leads. Each conductive lead may have contacts located at opposite ends thereof interconnected through an in intermediate conductive portion.
In accordance with at least one alternative embodiment, the primary ground contacts are formed in V-shapes with a base attached to a body of the module ground shield and an apex located distally from the body. Optionally, the primary ground contact may surround the secondary ground contact, while the primary and secondary ground contacts move independent of one another. Optionally, the primary and secondary ground contacts may have first ends mounted to a body of the module ground shield and second ends located at first and second distances, respectively, from the body with the first distance being greater than the second distance. As a further alternative, the primary and secondary ground contacts may be adapted to electrically engage a corresponding header ground shield on the header contact. The primary ground contact may have a length sufficient to electrically engage the header ground shield proximate a base of the header ground shield. The secondary ground contact may have a length adapted to electrically engage the header ground shield at an intermediate point along a length thereof or proximate the outer tip of the header ground shield.
In accordance with a further alternative embodiment, the connector assembly includes a cover mounted to each terminal module. Optionally, the cover may include at least one differential shroud enclosing an associated differential pair of contacts. Each shroud may have at least one open face exposing one of the top and bottom sides of the contacts. As a further alternative, the cover may include multiple differential shrouds receiving corresponding differential pairs of contacts. Each shroud may include a floor, sidewall, and a center wall to form separate channels to closely retain each contact. As a further alternative, the cover may have an open side facing and located immediately adjacent the primary and secondary ground contacts.